Means for regulating temperature.



J. C. WILSON & H. N. PACKARD.

MEANS FOR REGULATING TEMPERATURE.

APPLICATION FILED AUG. I6. 1913.

Patented A r. 2, 1918.

7 Mi 1 n DfGFEES FA IIRE/IHE/ 7' UNITED STATES PATENT OFFICE.

JOHN 0. WILSON AND HORACE N. PACKARD or WISCONSIN.

F MILWAUKEE, WISCONSIN, ASSIGNOBS TO THE CUTLER-HAMMER MFG. 00., OFMILWAUKEE, WISCONSIN, .A CORPORATION MEANS FOR BEGUL ATING TEMPERATURE.

Specification of Letters Patent.

Patented Apr. 2, 1918.

Application filed August 16, 1913. Serial no. 785,120.

' To all whom it may concern:

Be it known that we, JOHN C. WILSON and Home N. PACKARD, citizens of theUnited States, residing at Milwaukee, in the county of Milwaukee andState of Wisconsin, have in-vented new and useful Improvements in Meansfor Regulating Temperature, of

- which the following is a full, clear, conter resistance is arranged inadvance of said heating element and hence serves as a measure of thetemperature of the fluid before the heating thereof. A similar electricthermometer resistance is arranged in the rear of said heatingelement'and serves as a measure of the temperature. of the fluid afterheating. Bymeans of a control device in connection with these twothermometer resistances, the electrical energy supplied to the heatingelement is automatically regulated so that the heat dissipated therebywill cause a constant temperature difl'erence to be maintained betweenthe two points where the thermometer resistances are located.

()ne object of the invention is to provide an improved thermal controlmethod an'd apparatus such as may be used .in a meter I of the typeabove described.

Another object is to provide an improved thermal measurin method andapparatus.

Another object is to provide a method of and apparatus for obtainingaccurate thermal measurements.

Another object is to provide animproved method of and apparatus formaintaining a predetermined temperature in" a; medium, or apredetermined temperature dliferencebetween two points.- r

Another object .is to provide a thermal fluid meter having improvedthermal controlling and measuring means.

Another object is to provide an improved 7 or conduit 1, and flowsmethod of and apparatus for accurately measuring the flow of a fluid.

Another object is to provide a method of and apparatus for fluidmeasurement wherein the inaccuracies introduced by the variations in thephysical condition of-the fluid are reduced.

Other objects will appear as the specification proceeds.

In the accompanying drawings we have illustrated, somewhatdiagrammatically in Figure 1, the embodiment of the invention referredto above. Fig. 2 is a sectional elevation of the auxiliary resistanceand it's casing. .Fig. 3 is an explanatory diagram.

The moving body of steam, gas, or other fluid is directed through asuitable chamber astthe heating resistance 2, the latter beingpreferably uni- W formly disposed across the conduit. Said heatingresistance may assume various for1ns .-b ut as the form of theresistance forms nopart of the present invention, said resistance isillustrated'only diagrammatically. The thermometer resistances 3 and v 4are also illustrated only diagrammatically,

and in practice are uniformly disposed across the conduit. The ohmicresistance of thermometer resistance 3 is a measure of the temperatureof the incoming fluid, and the ohmic resistance of thermometerresista'nceel is a measure of the temperature of the fluid after it hasbeen heated.

The resistances 3 and 1' areconnected in two of the legs of aVVheatstone bridge, and

hence are balanced against each other. The heatlng reslstance 215connected to the mains 5, 6, in series w th a regulating resistance 7.The resistance 7 may be regulated to vary the heating effect of theresistance 2. The regulating means is only diagrammatically illustratedas any suitable means may be used for this purpose. For instance,the-resistance 7 may be varied by means of the control device shown inthe above mentioned patent to Thomas to vary the heating effect. TheWheatstone bridge also receives current from said mains, as shown, andhas resistances 8, 9, in the-other two legs thereof. An adjustableresistance 10 is connected in series with the thermometer resistance 4and an auxiliary resistance 11-is connected in series with thethermometer resistance 3. The auxiliary resistance may be termed atemperature difference resistance, for reasons hereinafter explained. Asecond resistance 12 is also connected in series with said thermometerresistance 3.

In meters of this character as designed heretofore, the resistance 11has been arranged outside of the conduit 1. When the fluid is beingheated, the diiference in the ohmic resistance of the two thermometerresistances 3, 4, is balanced by the resistance 11 connected in serieswith the former. The rheostat 7 is automatically controlled by suitablemeans such as shown in the above mentioned Thomas patent to vary thecurrent flowing through the heater 2, in such a manner as to maintainconstant the difference in temperature of the two thermometerresistances. Said thermometer resistances are similar in constructionand are made of the same resistance material, as it is desirable thattheir resistances be equal when their temperatures are equal, throughoutthe working range of themeter. With fluid flowing through the conduit,with the heater circuit broken so that no heat is being dissipated fromthe heater unit, and with the resistance 11 short-circuited by means ofa switch 13 or plug usually supplied tor the purpose, the \Vheatstonebridge will balance it it has been properly adjusted by means of theadjustable resistance 10. The condition of proper balance is indicatedby the galvanometer 14. Similarly, when the meter is in operation, theWheatstone bridge is also at a balance, the combined ohmic value ofresistance 11 and thermometer resistance 3 being just equal to the ohmicvalue of the thermometer resistance .4, the resistance of the latterbeing now greater, due to the heat imparted thereto by the-heated fluid.Any deviation trom the predetermined constant temperature difl'erencecauses an unbalancing of the system and is indicated by thegalvanometer, whereupon the energy dissipated in the form of heat isvaried to restore the balance. It will be seen that the energydissipated is a measure of the flow of the fluid. If more gas isflowing, it will require more energy to maintain the constanttemperature difference. If less gas is flowing, less energy will berequired. By the use of a-wattmeter in conjunction with suitablecalibration curves, the flow of the fluid may be readily determined,regardless of variations in temperature and pressure thereof.

The thermometer resistances are constructed preferably of nickel wire.The temperature-resistance curve of nickel and of a number of othermaterials suitable for the present purpose is not a straight line but acurve as shown in Fig. 3. In Fig. 3 the abscissae represent degreesFahrenheit and the ordinates represent resistance in ohms. The solidline represents the temperature-resistance curve of a material such asnickel. It will he noted that the increment a-b representing theincrease in resistance per given increase in temperature increases asthe temperature increases. For instance, at 60 a two degree-increase intemperature will cause an increase in resistance represented by thedistance a? At 80, however, the same temperature rise will cause agreater increase in resistance represented by the distance a-?). It willbe noted that the value of a?)' is greater than a-b because the slope ofthe curve at B is greater than at A. There are, however, materials forwhich this increment decreases as the temperature increases and ofcourse the thermometer resistances might be made of such material. Thetemperature-resistancc curve of such a material is represented by thedotted line which is convexed upwardly instead of downwardly. The slopeof such a curve is greater at A than'at B.

The above characteristic of nickel and similar materials tends toproduce an error in the reading of the meter because the temperature ofthe incoming fluid varies. For instance, if the fluid reaches the meterat 60 and is heated two degrees by the heater the ohmic value of theentrance thermometer resistance will be represented by a and that of theexit thermometer resistance will be represented by b. If, howet'er, thefluid reaches the meter at 80 and is heated two degrees by the heaterthe ohmic value of the entrance thermometer resistance will berepresented by a' and that of the exit thermometer resistance will berepresented by b. As above stated the value of ab representing thedifference in resistance between the thermometer resistances when thefluid is heated from 80 to 82 is greater than the "alue of a-brepresenting the difference in resistance between the two thermometerresistances when the fluid is heated from 60 to 62.

Therefore the difference in ohmic resistance between the .twothermometer resistances is greater for higher temperatures than forlower temperatures even though the fluid be heated the same amount. forall temperatures of the incoming fluid. This variation in the differencein resistance between the two thermometer resistances for differenttemperatures should be compensated for in order to make the meter readaccurately. This is one function of the resistance 11 as willhereinafter appear.

If the temperature of the approaching fluid were always the same theconstant difference in resistance between the two thermometerresistances would always correspond to a certain value of resistance andthe resistance 11 would accurately correspond to said constantdifferenceof resistance even if it were a resistance of fixed value. However, thetemperature of the incoming fluid usually varies thus causing thedifference in resistance between the thermometer resistances to "ary fora given rise in temperature as above explained, and therefore theresistance 11 should not be of a fixed value.

In order to obviate the error in" the calculations or registrations ofthe meter, due to the fact that the temperature resistance curve is nota straight line, the temperature difference resistance is constructed ofa material which will vary its resistance when the temperature varies insuch a way as to compensate for the above described varying differencein resistance between the two thermometer resistances for differenttemperatures. This-resistance is then mounted withln the conduit, asshown 111 Fig. 1, 1n-

stead of outside of the same, and hence it is subjected to the samevariationsin temperatureas those to which the thermometers aresubjected. Said resistance may be mounted either in front of or behindthe heating element, as its function is to change its resist ance withchanges in the absolute tempera.- ture of the gas rather than withchanges in the relative temperatures of two points therein. We locate itpreferably, however, in advance of said heating element.

' When the meter is in operation, the variation in the resistance of thetemperature difference -resistance off-sets the error which wouldotherwise be caused -due to the opera-' tion ofthe meter throughoutdifferent temperature. ranges. In other words, when the resistance ofthe entrance thermometer is low, the resistance of the temperaturedifference resistance is also low. hen the resistance oftheentrance'thermometer is high, the resistance of the temperaturedifference resistance is higher-than formerly. Hence,

the flow of the fluid may be very accurately determined for all workingconditions.

For many fluids the specific heat of the standard unit of measurement,which is usually a cubic foot under given conditions of temperature andpressure, is very nearly constant for all working ranges of temperatureand pressure. So long as this specific heat is constant and so long asthe temperature rise is kept constant, the electrical energy measured bythe Wattmeter is a direct measure of the rate of flow of the fluid. Theinvention, as described above, provides means for maintaining a constanttemperature difference withresistance thermometers under conditions thattend to cause this temperature'difi'erenceto depart from a con stant.

Under some conditions, the specific heat of the fluid does not, ineffect, remain constant however, underdifferent conditions oftemperature and pressure. For example,

let us assume that a saturated fluid at 7 60 millimeters pressure and 60degrees F. be heated to 100 degrees F. Its specific heatat eithertemperature is'nearly the same, but if it is allowed to absorb all theaqueous vapor that it will hold at 100 degrees, that is, if it absorbsadditional aqueous vapor until it is saturated at 100 degrees, eachoriginal cubic foot of fluid will carry through the meter this addedquantity of aqueous vapor. This added vapor will require an additionalamount of heat to raise its temperature the fixed amount and the meterwill read too high. It is desired in commercial work that specific heatcorrespondingly increases, the

temperature differcnce can be correspondingly decreased, the meter willrecord correctly. This is apparent from the fundamental equation,

qua e ea s heei reaeeslieracs Constant From this equation it is seenthat if the temperature difference can be decreased by the samepercentage as the specific heat is increased, the meter will stillrecord correctly. This is true, of course, regardless of whether watervapor or other vapor is contained in the fluid.

Now with thermometer resistances having a straight linetemperature-resistance curve, a temperature difi'erence resistance canbe so designed as to compensate for this variation in specific heat dueto water vapor or to similar causes. For example, the variation inspecific heat due to water vapor is a function of temperature of thefluid; that is, the specific heat increases as the temperature of thefluid increases. By making the temperature difference resistance of amaterial which decreases its resistance with increase in temperature andputting. this resistance in the fluid, the variation in temperature risein the meter due to this variation in the temperature differenceresistance may be made to compensate for the variation in the specificheat of the fluid.

As described above, if the thermometer resistances are of nickel, and ifa constant temperature difference is to be maintained in the meter asthe temperature of the fluid is increased, the temperature differenceresistance must be increased. If the fluid contains water vapor,however, and if the variations in specific heat, due to the presence ofthis water vapor, are to be compensated, the value of-the temperaturedifferencemust be decreased as the temperature increases. It 'thennickelwire thermometers are employed =ki'lowatts.

in the measurement of saturated fluids at varying temperatures, thevariation in temperature difference due to the curvature of thetemperature-resistance curve for the thermometers, tends to compensatefor the variation in the specific heat of the gas due to the presence ofwater vapors at different temperatures. By making the temperaturedifference resistance of the proper materials and so locating it thatthe temperature varies with the temperature of the fluid, these .twoerrors may be entirely compensated or sufliciently compensated forpractical results.

It is assumed, therefore, that the resistance 11 is of such material asto accomplish the above results. A resistance suitable for this purposewould be one constructed of nickel and manganese, for example, part ofthe resistance wire being of nickel and the other part of manganese, therelative proportions of which may be varied to meet varying conditions.In practice the resistance 11 is mounted independently of thethermometers. One form of support therefor is shown in Fig. 2, inwhichsaid resist ance is completely inclosed Within a metallic tube orcasing comprising a head 15 having screw-threaded engagement with thewall 1 of the meter housing and having a metal tube 16 fitting withinsaid head and preferably sweated thereto. Said tube is closed at itsdistant end by a metallic plug 17. The resistance is mounted on asuitable support carried by a screw-threaded rod 18, the latter passingthrough openings in a pair of insulating disks or blocks 19, 20.Suitable conductors 21 pass through these blocks through a pair ofopenings in each, the openings in one being preferably offset withrespect to the openings in the other, and the ends of said conductorsbeing electrically connected with the resistance. The other ends of saidconductors are received within suitable openings in an insulating disk22, which, together with a second insulating disk or plug 23, is securedin the outer end of the head 15. Conductors 24 extend through suit-ableopenings in the disk 23 and are electrically connected to theconductors21, the space between said disks being filled preferably with somesuitable insulating compound such as pitch.

With the above described arrangement it will be seen that the resistance11 may beconveniently. located at any desired point within the meterhousing or other structure. Furthermore, its easing may be readily re--moved. simply by unscrewin it from the separate and independent of thethermometers, because, as above stated, it is desirable to balance thethern'iometers against each other with the heating circuit broken andwith said resistance short-circuited in order to check the zero balanceof the thermometers from time to time during operation, and this may bereadily accomplished with such an arrangement. the short-circuiting ofsaid resistance be accomplished from the recording panel or otherconvenient point outside of the meter housing. Such operation isfeasible with the arrangement illustrated in Fig. 1, as the leads fromsaid resistance may extend as far as necessary to reach a convenientlocation. Although said leads may in certain cases be of considerablelength such that their resistances are an appreciable factor as comparedwith the resistance of the coil itself, nevertheless, since theresistance of said leads can be made the same, the resistance of oneoffsets the resistance of the other, regardless ofwhich lead isconnected as part of the circuit by means of the switch 13. It will alsobe noted in connection -with said switch that the latter is soconstructed in regard to the'width of its blade that the movement.theicof from one position to the other never opens the circuit throughthe leg of the \Vheatstone bridge in which it is connected. Such anopening of the circuit would be objectionable, as the galvanometerneedle would be thrown over to one extreme position, which operationmight result in burning out certain of the coils.

Vhile the above described system of regulation is illustrated inconnection with a fluid meter, it is apparent that it may be used tomaintain a predetermined (either constant or variable) temperaturedifference between any two points. It is therefore an example ofmaintaining a predetermined difference in temperature which tends tovary with actual temperatures. As a further example, it might be used tomaintain It is also desirable that the temperature of a furnace apredetermined amount above the atmospheric temperature by regulating theheat supply, or it might be used in various other relations in the arts,which will rea-dly suggest them selves. It will be seen, furthermore,that the temperature of a given medium may be maintained bythe use of asingle thermometer resistance located in said medium and an additionalthermometer resistance made of a material having a constant ohmicresistance corresponding to the temperature to which the temperature ofthe medium is referred. It is not essential that the two thermometerresistances be located necessarily in two different mediums, but merelythat one thermometer serve as a measure of a certain temperature andthat said tem- 180 perat ure be compared with some other tempreviouslydescribed, but may be varied mechanically in accordance with apredetermined law, or it may be varied manually. It is apparent, ofcourse, that in any application of the temperature differenceresistan'ce, that said resistance need not necessarily be subjecteddirectly to the same a physical contact with the fluid as the thermometer resistances, the important point being that said resistance besubjected to the same temperature variations as those which afl'ect saidthermometer resistances. The invention accordingly, as above emphasized,is not limited to the particular embodiment thereof described andillustrated, as we desire to cover in the appended claims whatever othersuitable means may be devised for accomplishing the desired resultswherever said means fall within the scope of said claims.

What We claim as new and desire to secure by Letters Patent of theUnited States is:

1. A system of control for regulating the temperature of a given medium,comprising a resistance element whichserves as a measure of thetemperature of said medium, and means other than said resistance elementfor varying the resistance of the circuit thereof.

2. A system of control for regulating the temperature'of a given medium,comprising a resistance element which serves as a measure of thetemperature of said medium,

means controlled by variations in the current flowing through saidresistance element due to variations in the resistance thereof forautomatically varying theheating of said medium, and means other thansaid resistance element for varying the resistance of the circuitthereof as the temperature of said element changes.

3. A system of control for regulating the temperature of a given medium,comprising a plurality of resistance elements one of which serves as ameasure of the temperatureof said medium and the other of which servesas "a standard with respect to which the temperature of said medium isto be regulated, means controlled by variations in the resistance of thecircuit of one of said resistances for automatically varying the heatingof said medium, and means for I varying the resistance of the circuitofone of said resistance elements as its temperature changes.

4. A system of temperature control for regulating the difference intemperature between two mediums in accordance with a predetermined law,comprising a resistance element located in each'of said mediums andacting as a measure of the temperature thereof, means for automaticallyvarying the resistance of one of said resistance ele ments, and meansresponsive to said variations for effecting the desired temperaturediiference.

5. In a temperature control device, means for measuring-the temperatureof a medium with respect to some other temperature, comprising a pair'ofresistance elements, means for varying the temperatureof said mediumsaid means being controlled by said resistance elements, and means forvarying the resistance of the circuit of one of said-resistance elementsto control the temperature of said medium in accordance with apredetermined law.

6. In a temperature control device, a Wheatstone bridge, a resistanceconnected in one'arm thereof, and a second resistance connected inseries with said first resistance and so located that its temperaturevaries with that of said first resistance.

7 A system of temperature control for maintaining a predeterminedtemperature difl'erence between two mediums, comprising a resistanceelement located in each of the respective mediums acting as a measure ofthe temperature of said mediums, and means for automatically varying theresistance of the circuit of one of said resistance elements inaccordance with variations in the absolute temperature of one of saidmediums.

8. A system of temperature control for maintaining a predeterminedtemperature difference between two mediums, comprising a resistanceelement located in each of the respective mediums acting as a measure ofthe temperature of said mediums, heating means for maintaining. adifference in the relative temperatures of said mediums, means forautomatically varying the resistance ofthe circuit of one of saidresistance elements in accordance with variations inthe absolutetemperature of one of said mediums, and a regulator for said heatingmeans controlled by said resistance elements.

9. Means for compensating for variations in the specific heat of gasesdue to variations in temperature, comprising a suitable resistancematerial subjected to the said variations in temperature, whereby itsresistance varies accordingly, and heating means for said gasesregulated by said variations in resistance.

10. In a fluid meter, a heating element for imparting heat to the fluidflowing therethrough, two resistance thermometers ar ranged one on eachside of said heating element, and means for automatically varying theresistance of the circuit in which one of said thermometers is connectedin accord ance with variations in the temperature of I 11. In a fluidmeter, a heating element for imparting heat to the fluid flowingtherethrough, two resistance thermometers arranged one on each side ofsaid heating elemc nt, and means for automatically varying theresistance of the circuit in which one of the thermometers is connectedin accordance with variations in the temperature of the fluid to beheated, said means eon'iprisinga resistance element which is subjectedto the same variations in temperature as said thermometer.

12. In a fluid meter, a heating element for imparting heat to the fluidflowing therethrough, two resistance thermometers arranged one on eachside of said heating element, and means for automatically varying theresistance of the circuit in which one of the thermometers is connectedin accordance with variations in the temperature of the fluid to beheated, said means comprising a resistance element arranged in theflowing steam or gas.

13. In a fluid meter, a pair of resistance thermometers for measuringthe difference in temperature of two different points in a flowing bodyof fluid, said thermometers being substantially similar and constructedof the same resistance material, and an additional resistance connectedin series with the one normally having the least resistance and arrangedin said flowing body of steam or gas, said additional resistance beingconstructed of material which varies its resistance with variations intemperature to com pensate for the variations in the resistance value atdifferent temperatures which represents the temperature differencebetween the thermometers.

14. In a fluid meter, a pair of resistance thermometers for measuringthe difference in temperature of two different points in a flowin bodyof fluid, said thermometers.be

ing su stantially similar and constructed of the same resistancematerial, and an additional resistance of difi'erent material than thethermometers, said resistance being connected in series with the onenormally having the least resistance and subjected to the temperature ofsaid flowing body of fluid before the same is heated.

15. In a temperature control device, a resistance subjected to thetemperature of a given medium, and means for rendering said resistanceoperative at will by connect ing it in circuit or disconnecting it therefrom, saidmeans including a switch and conductors of equal resistanceextending from the terminals of said switch to the terminals ofsaidresistance.

' 16. In a temperature control of the class described, a resistancesubjected to the temperature of the medium to be controlled, and aswitch controlling the connections to said resistance, said switchcomprising a plurality of contacts and a movable switch blade adapted tomomentarily bridge both contacts when moving from one to the other.

17. The method of determining the rate of flow of fluids which consistsin imparting heat to the flowing stream and automatically varying therate of heat dissipation to'maintain constant the rise in temperaturebetween two thermometers arranged one on each side of the heatingelement and automatically adding to the resistance of the coolerthermometer a variable resistance to compensate for variations whichwould otherwise occur within the range in temperature throughout whichthe meter is effective.

18. The method of compensating for variations in the physical propertiesof a given medium, due to temperature changes therein, which consists insubjecting to said temperature changes a resistance which varies invalue in the same characteristic manner as said physical properties andin -modifying the temperature of said medium in accordance with saidvariations in reslstance.-

19. Means for eflectmg accurate thermal measurements, comprising aresistance responsive to the temperature of the medium being measured,said resistance having portions of diflerent physical characteristics soselected and arranged that the difference in ohmic resistance betweensaid resistance and a standard corresponds to a fixed temperaturedifference between the medium and that of a standard through a desiredrange of temperatures.

20. Means for measuring the temperature change of a medium comprising apair of electrically connected thermometer resist ances and acompensating resistance associated with at least one of the thermometerresistances to compensate for errors due to variations in the physicalcondition of the medium.

21. A system of control for regulating the temperature of a given mediumcomprising a resistance element which serves as a measure of thetemperature of said medium, and a means other than said resistanceelement for varying the resistance of the circuit thereof as thetemperature of said element changes.

V 22. A' system of control for regulating the temperature of a givenmedium, comprising a resistance element which serves as a measure of thetemperature of said medium, and means other than said resistance elementfor automatically varying the resistance of the circuit thereof.

23. The method of determining the rate of flow of fluids which consists1n causing a heat-interchange between a body and the fluid,automatically varying the rate of heat interchange to maintain aconstant temperature change between two thermometer resistances arrangedone on each side of said body, and automatically adding to theresistance of one of said thermometer resistances a variable resistanceto compensate for variations which would otherwise occur within therange in temperature through out which the meter is effective.

between two thermometer resistanceslocated therein, and automatically"adding to the resistance of one of said thermometer resistances avariable resistance to compensate 15 scribed our names in the presenceof two 20 witnesses.

JOHN C,- WILSON. HORACE N. PACKARD. Witnesses:

C. R. POE, F. H. HUBBARD.

